Radar systems often utilize a wide, instantaneous bandwidth to enable high range resolution. Radar systems further implement frequency hopping in a burst to burst fashion over a broad agile band to enhance target detection. Radar operating bands are being shared by an increasing number of users, including governmental and commercial mobile communications systems. Other users' transmissions may be considered EMI relative to an intended transmission due to the fact that such “other” transmissions cause undesired interference in the “intended” transmission's operating band. In an attempt to avoid EMI, current radars typically implement a clear channel search function to determine frequencies within an operational band having minimal EMI. Implementation of a clear channel search function involves developing a clear channel map (commonly referred to as a least jammed map or least interference map) over a period of many scans. In this fashion, a clear channel map may take up to several minutes to construct. As the clear channel search function performs the scans, received EMI is integrated over time, thereby showing directions and frequencies on which EMI is detected. A scheduler is configured to process the clear channel map data output frequency, bandwidth, and timing information for EMI-free or minimal EMI signal transmission. Thus, the radar system may avoid transmission on frequencies and directions on which EMI above a threshold value was detected. Because the clear channel search function integrates EMI over a period of time, a frequency may be indicated as containing EMI even though for periods of time much greater than radar dwells, the same frequency contains little or no EMI. For example, users transmit on various frequencies, thereby causing EMI. However, such transmissions do not occur continuously. A police radio may transmit intermittently, typically shutting off for at least one half second between transmissions. Because radar coherent dwells are generally on the order of 1 to 50 milliseconds (ms), a radar could transmit on a frequency also used by another, such as a police radio frequency, by only transmitting during these short, interference-free time intervals.
Alternative systems and methods for mitigating EMI are desired.